(1) Field of the Invention
The present invention relates to a magnetostrictor which transduces an electric energy to a mechanical energy and produces a vibration of gas or liquid. More particularly, it relates to a magnetostrictor comprising amorphous metal material as its magnetic component, which is usable for such variant devices as an ultrasonic cleaning machine, a frequency agile transmitter-receiver for microwave, a magnetostrictive delay device, a sensor utilizing magnetostrictive characteristics of the material etc.
(2) Description of the Prior Art
Presently, materials, such as Ni-Fe alloy(Magentostrictive coefficient .lambda.s=27.times.10.sup.-6), Fe-Co alloy(.lambda.s=70.times.10.sup.-6) Fe-Al alloy(.lambda.s=40.times.10.sup.-6), Mn-Ni ferrite(.lambda.s=-27.times.10.sup.-6) are known as highly magnetostrictive materials. But each of these prior materials is provided with a rather small coefficient of electromechanical transduction(K) which represents its transformation efficiency of electric energy to mechanical energy and which is the most important characteristic of the material to be incorporated in a magneto-strictor as an ultrasonic vibrator. For example, the K-values of Ni-Fe alloys, Fe-Co, Fe-Al and Mn-Ni ferrites range respectively from 0.2 to 0.3, 0.2 to 0.4, 0.2 to 0.3 and 0.2 to 0.3.
On the other hand, amorphous metal alloys are known as materials provided with generally a high permeability because they have a random array of atoms therein and no crystallomagnetic anisotropy. Especially Fe-base amorphous metal alloys are known to have rather large magnetostriction coefficients(.lambda.s) as 45.times.10.sup.-6 and soft magnetic properties which result in rather large coefficients of electromechanical transduction(K) of 0.8 or more. These Fe-base amorphous metal alloys are expected to be excellent materials for use as magnetic components to be incorporated in magnetostrictors. Further, variations(.DELTA.E) of Young's modulus(E) of these Fe-base amorphous metal alloys which are caused by bias magnetic fields are rather large values. For example, the .DELTA.E/E value of Fe-base amorphous metal alloys could be equal to 1.91. The mentioned characteristics of Fe-base amorphous metal alloys make these alloys useful for miniaturized magnetostrictive delay devices which are capable of a continuous electro-control, or a small-sized frequency-agility type of transmitter-receiver of a microwave because the resonant frequency of a device comprising a Fe-base amorphous alloy can be varied for its large value of .DELTA.E/E. Fe-base amorphous metal alloys are provided with an extremely high tensile strength as 300 Kg/mm.sup.2 and especially a Fe-base amorphous metal alloy comprising a small amount of Cr has a high corrosion resistance value of up to 10.sup.4 to 10.sup.5 times of a corrosion resistance value of a stainless steel, as well known. These highly magnetostrictive Fe-base amorphous metal alloys have excellent essential characteristics desirable for a practical material to be incorporated in a mangetostrictor. Many practical applications of these Fe-base amorphous metal alloys are described in Laid Open Patent Applications 49-112551 51-111698, 52-117002, 56-44203, 57-20076, 57-83997, 57-103499 and 58-5099.
But the descriptions in these Laid Open Patent Applications are silent about serious problems of the amorphous metal alloys to be incorporated in practical devices. That is, the thickness of an amorphous metal alloy is restricted, because a rapid quench of an alloy melt, the cooling rate of which is at least 10.sup.5 degrees/second is necessary. Because of the restriction, the thickness of Fe-base amorphous metal alloy sheets having a high magnetostriction ranges generally from 20 .mu.m to 40 .mu.m. It is necessary to laminate and bond a number of amorphous metal sheets to make a bar or a rather thick plate comprising amorphous metal material which is actually useful to be incorporated in a device such as an ultrasonic vibrator. But it has been found that the efficiency of a magnetostrictor comprising laminated thin amorphous sheets and a binder is extremely deteriorated, because the binding material becomes a dampener in it. The most important reason why a magnetostrictor comprising amorphous metal material is not practical is due to the mentioned problem of the lamination, although Fe-base amorphous metal alloys can be provided with a high magnetostriction, a high tensile strength, a high corrosion resistance, and a high variance(.DELTA.E) of Young's modulus(E) caused by a bias magnetic field and a large coefficient of electromechanical transduction(K). It is proposed to make binder layers between amorphous metal sheets in a lamination type of bulk material as thin as possible, to exclude the above-mentioned problem in the Japan Laid Open Patent Application 57-103499. But Japan proposed method in the 57-103499 is not practical, because a special polishing process using a special abrasive is required to reduce the surface roughness Rz of amorphous metal sheets produced by a conventional method to a value of 0.5 .mu.m to 1 .mu.m from an original value of 2 .mu.m to 3 .mu.m, in order to make the binder layers extremely thin.